1. Field
The present disclosure relates to a rechargeable battery. More particularly, the present disclosure relates to a structure of a case that houses an electrode group.
2. Description of the Related Technology
A rechargeable battery typically includes an electrode group that includes an positive electrode, a separator, and a negative electrode, a case that houses the electrode group, and an electrode terminal that is connected to the electrode group and that is drawn out to the outside of the case. The case can be formed with a laminate sheet in which a metal layer and a resin layer are bonded, and a rechargeable battery having the case is referred to as a pouch type battery.
A common pouch type battery is typically formed by fixing a positive electrode terminal and a negative electrode terminal by welding to a positive electrode uncoated portion and a negative electrode uncoated portion, respectively, of the electrode group, housing the entire electrode group, a part of the positive electrode terminal and the negative electrode terminal in the internal space of the case with an electrolyte solution. The battery is then typically sealed by bonding edges of the upper case and the lower case by thermal bonding.
However, in the above-described structure, a welding portion of the electrode group and the electrode terminal, a sealing portion of the upper case and the lower case, and a drawn-out portion of the electrode terminal are sequentially positioned at the outside of the electrode group. Therefore, because a portion that does not contribute to an actual battery reaction in the entire rechargeable battery occupies a large area, the entire volume is expanded. Thus, it is disadvantageous to form the rechargeable battery to have high capacity and a compact size.
Moreover, when thermal bonding the upper case and the lower case, the upper case is sealed to the lower case by deep drawing the upper case. In this case, because the edge of the upper case becomes weak by the deep drawing, the case can be easily damaged by an external impact, and thus reliability of the rechargeable battery is deteriorated.
The above is only provided to enhance understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.